1. Field of the Invention
The invention relates to a combustion power tool that performs a predetermined operation by utilizing a high pressure impact force generated upon combustion of flammable gas.
2. Description of the Related Art
Japanese non-examined laid-open Patent Publication No. 2004-358565 discloses a combustion power tool such as a nailing machine and a tacker, which is powered by a piston/cylinder-type internal combustion engine. In this known art, a combustion chamber is partitioned into a main combustion chamber and a secondary combustion chamber by a partition having communication holes. Combustion gas is burned in the secondary combustion chamber and then led into the main combustion chamber, so that flammable gas within the main combustion chamber is burned. By combustion pressure generated by this burning action, a piston member is moved to a front end side, so that a nail driving operation is performed on a workpiece.
In the above-described combustion power tool, after nail driving movement of the piston member, gas within the main combustion chamber is cooled so that pressure within the main combustion chamber is reduced to below atmospheric pressure (to a negative pressure). As a result, the piston member is returned to its initial position. Therefore, in such a construction, in order to reliably return the piston member to its initial position after nail driving movement, it is important to reduce the gas temperature within the combustion chamber. In this known combustion power tool, further improvement is required in cooling the gas within the main combustion chamber after nail driving movement of the piston member.